This invention relates to an improved method and apparatus for thermal disposal of waste material such as sewage, sludge, garbage or the like, involving drying and burning of the waste.
The economical and environmentally safe elimination of waste materials such as sewage sludge, special garbage or the like raises considerable difficulties. This is particularly true when such waste materials are burned in standard garbage incinerating systems which have grate firings. Grate firings must be operated with high excess air ratios, so that great quantities of flue gas having relatively low temperature arise. Great quantities of flue gas correspondingly require large and cost-intensive exhaust gas scrubbing systems. Further, it is possible in grate firings that the combustion temperatures at least temporarily fall below 1000.degree. C. At such temperatures, some dangerous toxins such as dioxins, do not yet decompose. Many valuable substances and/or noxious substances contained in the waste materials do not volatilize at such temperatures, so that such substances undesirably pass into the ash. Conventional garbage incinerating systems are uneconomical and environmental pollution can derive because of the emission of organic compounds and because of the ashes thereby arising are not leachingresistant.
An object of the present invention is to create a method with which waste materials such as, for example, sewage sludge, special garbage or the like, can be thermally disposed in an environmentally safe and also an economic fashion.
A further object of the invention is to provide a method and apparatus for the improved continuous treatment of waste materials which permit recovery of useful substances out of exhaust gases.
A still further object of the invention is to provide an improved method and apparatus for the treatment of waste materials which complies with high requirements of laws which pertain to maintaining discharge gases at a non-noxious level.
A still further object of the invention is to provide an improved method and apparatus for the treatment of waste materials such as garbage and sewage wherein materials are handled in a special sequence of steps at unique temperatures and in a unique separation and mixing so that an improved handling results which reduces costs and results in an environmental improvement over methods heretofore used.